Note: Descriptions are shown in the official language in which they were submitted.
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TANK WITH CONTAINMENT & OVERFLOW
s The invention is in the field of liquid storage containers and
in particular such liquid storage containers which provide
secondary containment of the stored liquid.
to
Liquid storage containers, or tanks, are commonly used to
store liquid for many industrial and commercial purposes.
Where hazardous or potentially damaging liquids are stored,
the tank assembly must include provision for secondary
~s containment of the liquid. It is desirable as well to
containing overflow from the tank.
Conventionally the secondary containment and overflow
provision are provided by a double walled tank, essentially a
2o tank within a tank. In conventional tank assemblies, any
overflow liquid from overfilling the primary tank is directed
into the secondary containment tank such that essentially the
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overflow tank and the secondary containment tank are the same
tank. Thus in the conventional tank assemblies there is no
secondary containment provision for the contents of the
overflow tank. Should the primary tank begin to leak, any
leaking liquid will be caught by the secondary containment
tank. For liquid to escape into the environment from the
primary tank two leaks must occur, one in the primary tank,
and a second leak in the secondary containment tank.
1o Liquid from any overflow tank, however, can escape into the
environment where only one leak occurs, that being in the
secondary containment tank.
It is also common at certain sites to require two tanks for
two separate liquids, such as at a petroleum well site, during
the winter, where a water storage tank is required as well as
a methanol tank to supply methanol which is circulated in the
lines to prevent freezing. Diesel fuel is commonly kept in
an auxiliary tank as well. Conventionally the auxiliary tank
2o is separate from the primary tank assembly. Transport of the
second auxiliary tank is problematic as it must be handled and
transported separately from the primary tank assembly. The
auxiliary tank is also not protected by any secondary
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containment system.
Insulated tank assemblies are often required for various
applications in extreme conditions.
SUi~iARY OF THE INVENTION
It is an object of the present invention to provide a tank
assembly with an overflow tank that is contained such that
io liquids leaking from the overflow tank do not escape into the
environment.
It is a further object of the present invention to provide a
tank assembly which includes storage tanks for two separate
liquids for easy transport, and where both tanks may be
protected by secondary containment such that liquid leaking
from either tank does not escape into the environment.
The present invention provides a liquid storage tank assembly
2o comprising a primary tank for storing a liquid; an overflow
tank operatively connected to the primary tank such that when
the liquid in the primary tank rises to a full capacity level
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of the primary tank, excess liquid flows into the overflow
tank; and a secondary containment tank enclosing the primary
tank and the overflow tank such that liquid leaking from the
primary tank or the overflow tank is contained in the
secondary containment tank.
The tank assembly may be configured in any convenient shape,
and may be provided with a contained, attached auxiliary tank,
and with insulation and heat if required.
In a second aspect the invention provides a liquid storage
tank assembly comprising a primary tank for storing a first
liquid; a secondary containment tank enclosing the primary
tank such that liquid leaking from the primary tank is
i5 contained in a containment chamber between the inner tank and
the secondary containment tank; a hollow base for supporting
the tank assembly, the hollow base attached to the secondary
containment tank to form a base chamber; and an auxiliary tank
for storage of a second liquid, the auxiliary tank fixed to
2o the assembly inside the base chamber. Where methanol is
stored in the auxiliary tank, containment is not critical, and
the auxiliary tank may share a wall with the base. Where
diesel or other hazardous products are stored in the auxiliary
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tank it may be a totally separate tank fixed inside the base
chamber such that liquid leaking from the auxiliary tank may
be contained in the base chamber.
DESCRIPTION OF THE DRAWINGS:
While the invention is claimed in the concluding portions
hereof, preferred embodiments are provided in the accompanying
detailed description which may be best understood in
1o conjunction with the accompanying diagrams where like parts in
each of the several diagrams are labeled with like numbers,
and where:
Fig. 1 is perspective view of an insulated tank assembly
1s embodying the invention;
Fig. 2 is a schematic side view showing the operation of
the tank assembly of Fig. 1.
2o Fig. 3 is a schematic end view showing the operation of
the tank assembly of Fig. 1.
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Figs . 4 and 4A are schematic top and side views of an
alternate vertical cylindrical embodiment;
Figs. 5 and 5A are schematic top and side views of an
alternate rectangular embodiment;
Figs. 6 and 6A are schematic end and side views
illustrating the location of the insulation in the tank
assembly of Fig. 1.
Figs. 7 and 7A are schematic end and side views
illustrating an un-insulated tank assembly.
Figs. 8 and 8A are schematic end and side views
illustrating an alternate tank assembly with no overflow
tank, and showing an economical auxiliary tank that is
not secondarily contained.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS:
Fig. 1 illustrates a liquid storage tank assembly 1 of the
invention comprising a primary tank 2 for storing a liquid L;
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an overflow tank 3 operatively connected to the primary tank
2 by an overflow port 4 such that when liquid L in the primary
tank 2 rises to a full capacity level F, excess liquid L flows
through the overflow port 4 and into the overflow tank 3.
Figs. 2 and 3 schematically illustrate the operation of the
tank assembly 1.
Typically secondary containment tanks are built around the
primary tank, with little or no actual gap between the two
1o tanks, or "skin on skin". The gap is exaggerated in the
illustrations herein for ease of demonstration.
A secondary containment tank 5 encloses the primary tank 2 and
the overflow tank 3 such that liquid L leaking from the
primary tank 2 or the overflow tank 3 is contained in the
secondary containment tank 5.
Conversely as well, should the primary tank 2 rupture such
that liquid L is leaking from the primary tank 2 into the
2o secondary containment tank 5, during filling the liquid level
could rise in both the primary and secondary containment tanks
2, 5 at the same time. When the liquid level in the primary
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and secondary containment tanks 2, 5 rises to a level
approaching a full capacity level F of the secondary
containment tank 5, excess liquid L flows through the overflow
port 4 into the overflow tank 3.
The overflow tank 3 thereby acts as an overflow for both the
primary and secondary containment tanks 2, 5 and the secondary
containment tank 5 acts as containment for both the primary
and overflow tanks 2, 3.
The primary and overflow tanks 2, 3 are formed by dividing an
inner tank 6 with a substantially vertical partition wall 7
into a first portion, being the primary tank 2, and a second
portion, being the overflow tank 3. The partition wall 7
defines the overflow port 4 in an upper portion thereof at a
level corresponding to the full capacity level F of the
primary tank 2.
The inner tank 6 is smaller than the secondary containment
ao tank 5, and is mounted inside the secondary containment tank
5 such that a containment chamber 8 is formed between the
tanks 5, 6 to contain liquid L leaking from a rupture in the
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primary tank 2 or overflow tank 3.
For convenience and economy of manufacture, the inner tank 6
and secondary containment tank 5 can be cylindrical and
mounted substantially concentrically in a substantially
horizontal orientation, as illustrated in Figs. 7 and 7A.
Alternatively the tank assembly 1 could comprise vertically
oriented cylindrical inner and secondary containment tanks 5,
io 6 as illustrated in Figs. 4 and 4A, or rectangular tanks as
illustrated in Figs. 5 and 5A. Many convenient shapes for
particular purposes could be employed to embody the invention,
and all such variations in shape are intended to fall within
the scope of the present invention.
is
The tank assembly 1 further comprises a hollow base 9 for
supporting the tank assembly 1. The hollow base 9 is attached
to the secondary containment tank 5 to form a base chamber 10,
having a base chamber floor 10f, two opposite substantially
2o vertical base chamber end walls 10e, two opposite
substantially vertical base chamber side walls 10s, and a base
chamber ceiling 10c. The base chamber ceiling comprises an
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outer surface of the secondary containment tank 5.
In the illustrated embodiment of Fig. 1, as seen in Figs. 6
and 6A, the tank assembly is insulated so as to thermally
isolate the primary tank 2 and base chamber 10 from an
ambient temperature, and further comprises a heater mounted
13 inside the base chamber 10 and operative to heat the base
chamber and a bottom portion 5b of the secondary containment
tank 5.
io
To allow effective heating of the liquid in the primary tank
2, the secondary containment tank 5 comprises a lower portion
5b below a mid-point M positioned immediately adjacent the
primary tank 2 in the conventional "skin on skin" orientation.
is This allows heat to pass relatively easily from the base
chamber 10 to the primary tank 2. To provide for insulation
of the primary tank 2, being the inner tank 6, an upper
portion of the secondary containment tank 5a above the mid-
point M is positioned to form a first insulation chamber 30a
2o between the inner and outer tanks 6, 5. The secondary
containment tank 5 is also positioned such that second and
third cylindrical insulation chambers 30b, 30c are formed
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between the inner tank 6 and secondary containment tank 5 at
opposite ends of said tank assembly 1.
The insulation chambers may be insulated with particulate,
foam, fibreglass batt, or other conventional insulation 14.
If the primary or overflow tanks 2, 3 leak into the secondary
containment tank 5, the insulation 14 may come into contact
with the leaked liquid. Insulation that is not subject to
damage may be used, or same may then require replacement.
io
The base chamber side walls lOs extend upwards from the base
chamber floor lOf to the mid-point M, approximately one half
way up the secondary containment tank 5 along each side
thereof. A layer of insulation 17 is also sprayed or
otherwise applied to an inner surface of the base chamber end
walls 10e and side walls 10s. The floor lOf is generally left
un-insulated but could easily be insulated if desired. There
is no insulation between the base chamber 10 and the secondary
containment tank 5, allowing heat from the base chamber 10 to
2o heat the secondary containment tank 5.
The illustrated embodiment provides an insulated tank where
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all the insulation is protected from damage by contact with
equipment and so forth by being inside the outer surface of
the tank assembly 1.
The tank assembly 1 further comprises an auxiliary tank 11 for
storage of a second liquid. The auxiliary tank is fixed to
the assembly 1 inside the base chamber 10 such that liquid
leaking from the auxiliary tank 11 is contained in the base
chamber 10. An access door 12 into the base chamber 10 is
io mounted above the base chamber floor lOf such that all liquid
stored in the auxiliary tank 11 can be contained in the base
chamber 10 at a level below the access door 12 should the
auxiliary tank 11 begin to leak.
Figs. 8 and 8A illustrate an alternate tank assembly 20
comprising a main tank 18 for storing a first liquid. A
secondary containment tank 5 encloses the main tank 18 such
that liquid leaking from the main tank 18 is contained in a
containment chamber 8 between the main tank 18 and the
Zo secondary containment tank 5. A hollow base 9 supports the
tank assembly 20. The hollow base 9 is attached to the
secondary containment tank 5 to form a base chamber 10. An
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auxiliary tank lla for storage of a second liquid is fixed to
the tank assembly 20 inside the base chamber 10. Auxiliary
tank lla is not protected by secondary containment, as base
chamber sidewall 10s, and base chamber floor 10f form a
portion of the auxiliary tank 11a. The auxiliary tank lla is
economical and could be safely used with non-hazardous liquids
such as methanol. Optionally the separate contained auxiliary
tank of Figs. 7 and 7A is available for hazardous liquids.
Overflow, insulation and heat could be provided for the
1o alternate tank assembly 20 as described above, and the
configuration could also be any convenient shape as described
above.
The foregoing is considered as illustrative only of the
is principles of the invention. Further, since numerous changes
and modifications will readily occur to those skilled in the
art, it is not desired to limit the invention to the exact
construction and operation shown and described, and
accordingly, all such suitable changes or modifications in
2o structure or operation which may be resorted to are intended
to fall within the scope of the claimed invention.
